<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style type="text/css">
        #result
        {
            width: 200px;
            height: 200px;
            border: solid 1px #903;
        }
    </style>
    <script type="text/javascript">
        window.onload=function()
        {
            //获取元素
            const result=document.getElementById("result");
            //绑定事件
            result.addEventListener("mouseenter",function(){
                //console.log("test");
                //1.创建对象
                const xhr=new XMLHttpRequest();
                //2.初始化 设置类型与URL
                xhr.open("POST","http://127.0.0.1:8000/server");
                //设置请求头
                xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
                xhr.setRequestHeader("name","atguigu");//此变量属于自定义，所以会报错（有安全机制）
                //3.发送
                xhr.send("a=100&b=200&c=300");
                //send的参数可以是任何形式的，只要服务器能处理
                //4.事件绑定
                xhr.onreadystatechange=function()
                {
                    //判断
                    if(xhr.readyState === 4)
                    {
                        if(xhr.status>=200&&xhr.status<300)
                        {
                            //处理服务端返回的结果
                            result.innerHTML=xhr.response;
                        }
                    }
                };
            })
        };
    </script>
</head>
<body>
    <div id="result"></div>
</body>
</html>